Duplex telegraph system



July 56:19.27.

IIHIIIIIIHIQ Hm-PL J. H. BELL DUPLEX TELEGRAPH SYSTEM Filed Sept. 29. 1924 Wye/272x Jam /7. 56// Patented July 26, 1927.

UNITED STATES PATENT OFFICE.

JOHN H. BELL, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR T WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, Y., A CORPORATION OF NEW YORK.

DUPLEX TELEGRAPH SYSTEM.

Application filed September 29, 1924. Serial No. 740,487.

This invention relates to telegraph sys-' tems and more particularly to duplex telegraph systems.

It is the object of the present invention to facilitate the uninterrupted operation of a telegraph or other signaling system having a balancing artificial line by indicating the existence of an unbalance condition.

According to the above object, the invention provides for the coordination of apparatus in a system of this kind for indicating the existence of an unbalance condition before it becomes great enough to cause interference with the operation of the system. Specifically, the invention provides electroresponsive devices, and indicating means associated with the telegraph circuit for informing an attendant of any lack of balance between the real and artificial lines.

The invention is illustrated diagrammatically in the accompanying drawing and for the sake of clearness only so much of the system has been shown as is necessary for a clear understanding of the invention.

Referring to the drawing, a line conductor 5 is shown which extends between two remotely situated stations where duplicate equipment is located. Connected to the line conductor 5 is a pole changer or transmitting key 8 which functions to impress on the line conductor 5 signaling current impulses of opposite polarity. Arranged with the line conductor 5 are resistance units 6 and 7 serving as the ratio arms of a bridged duplex formed through an artificial line AL and the real line 5. In order that impulses transmitted from the opposite end of line 5 may be received at the station shown, a relay 9 is connected between the line 5 and the artificial line AL. As is well understood in connection with the operation of duplex telegraph circuits, changes in the polarity of the impulses transmitted over the line 5 due to the operation of the pole changer or transmitting key 8, do not pro duce any effect. on the relay 9 but the arrangement of the circuits is such that this relay responds to all incoming impulses. Operatively connected with the relay 9 is a telegraph sounder 10 or other recording device.

Coming now to the particular features of the invent-ion, a relay 11, which has been shown as a polarized relay is connected to the apex of the ratio arms 6 and 7, Connected in the energizing circuit of this relay is a condenser 12 which is charged and dis charged in accordance with the position of the pole changer or transmitting key 8. Upon the reversal of the impulses applied to the apex of the ratio arms 6 and 7, the relay 1]. will be caused to reverse the position of this armature, that is, the armature will engage first one contact and then the other. Connected to the contacts of this relay 11 are windings 1 3 and 14 of a control relay of indicating means such as lamps 16 and 17. Due to the adjustment of this relay, its armature is held in a neutral position and requires the establishment of an appreciable magnetic effect before it is caused to engage either of these co-operating contacts. The armature of the relay 11 is connected to point 18 while the windings 13 and 14 are connected through a common path to point 19. It is thus seen that the operation of relay 15 due to the energization of either of these windings 13 or 14 will result only upon the existence of a difference of potential between these two points 18 and 19. It is also noted that the windings 13 and 1 1 are each of a large number of turns in order to make it highly sensitive. Therefore, for small differences of potential between the points 18 and 19, the armature of relay 15 will be caused tomove to engage one or the other of these contacts, thereby effecting the operation of either lamp 16 or 17 The indicating device just described can be applied to a number of duplex circuits in sequence by arranging the system so that the indicating device will be connected to the various duplex circuits. For accomplishing this feature, switching means 20, 21 and 22-, cooperating with a number of contacts, may be provided for connecting the respective elements constituting the indicating device to the various duplex circuits. These switches 20, 21 and 22 may be arranged to engage the contacts extending to the other duplex circuits at definite intervals. In other words, the indicating device may be connected with the difi'erent duplex circuits periodically, in this way a check might be made of the balance from time to time.

lVhen the pole changer or transmitting key S is operated for transmitting impulses over the line 5, the relay 11 follows the which functions to control the operation Cir operation of thiskey and,;inasnuu:h as it is quiclc acting, connects the windings 13' and 1 1 alternately with the point 18 upon each reyersal therepf. Should the real line 5 be aociiiratiely balanced with th'i artificial line AL, no difference of potential exists be tween the points 18 and 19. Therefore, neither of the windings 13 and 14 is encrgized and in consequcnceneithcr of the indicating lamps l6 and 17 is operated. I \Vhen this condition exists, the impulses incoming reversing-in polarity andas theyi'will not be inun'ison with the movements of relay 11, they will pass through both windings 13 and l t-of relay 15 and so will tend to cancel outand produce no magnetic efiect. However, should the resistance" of the rear line 5 be increased due to a change from a wet to a dry condition, a dilferencc of potential will exist'betwecn points 18 and 19 and due to the rapid reversal of the armature'ol relay 11 and the passage of current through the windings 13 and 14 and the cumulative action of thesewindings, the armature thereof will he moved to engage one or the other of its contacts depending upon the polarity of the applied current For the sakeof illustration, assume that the polarity of the applied current is negative, in which cascthe relay formed of the windings 13 and 14 will be moved to cause the illumination ol' lamp 17.. The lighting of lamp 17 serves as an indication to the attendant that the artificial line AL should be adjusted to correct or compensate forthe changes in the realrline. Conversely, when the. resistance of the real line is reduced, due toa change from a dry to a wet condition, and due to the constant reversal of the armature of relay 11, and the cumulative action of windings 13 and 14, the magnetic etfect pro,- ducedwill be suflicientto cause/the engagementof the jarmature with the contact connected to indicating. lamp 16, The illumination of this" lamp 16 will, like the lightingot-lamp17,*indicate to the attendant the existence of an unbalanced condition.

hen the distantrstation ceases to send, a considerable difference of potential may exist between the points18 and '19 but so long as relay 11 is operating, theaggregate efl ect of the distant station current upon the actionof relay 9 will be practically nil; dVhen bot-li stations are idle, it is of course necessarythat the device he in its normal or; unoper'ated posit-ion. This feature is ac complishcd through the provision of condenser '12 and the use of a relay having a normal or central position for its armature. When the indicating means isused in conjunction with a number of duplex circuits, theswitching means 20, 21 and 22 would be operated to connect theindicating means to the other duplex circuits in succession,

from the dist-a'ntstation will be constantlytion 'of the operation of the system that, the

balance may he quickly determined and the artificial lineAL adjusted to correct for.

any lack of balance without interrupting or in any wayrintcrfering with the operation of the system. Also the existence of lack of balance between the real and artificial lines will be indicated before the degree of'une balance becomes such as to cause entire failure of the telegraph receiving mechanism. V i

It is, of course, obvious that various modifications may be made without departing from the spirit and scope of the present invention. It is therefore not intended that the invention should be limited to the specific arrangement shown but only by the appended claims.

- What is claimed is:

1. In a telegraph systenna pair of ratio arms,.a real and an artificial line connected to opposite ends of said ratio arms, transmitting and receiving.mechanisms associated therewith, a relay having a pair of windings, each of said windings being normally disconnected from its associated circuit, inclicating means controlled by said relay, and switching means responsive to each rcveisal of said transmitting mechanism for alternately connecting the windings of'said relay hetween'the points of connection of said real and artificial lines.

2. In a telegraph system, a plurality of duplex circuit-s, duplex balance indicating means comprising an electromagnetic device responsive to each reversal of the transmitting mechanism, switching means controlled by said electromagnetic device and responsive to currents resulting through unbalance conditions between the real and artificial lines, indicating means controlled by said switching means for indicating the character ofsuch unbalance,and means for connecting said indicating means with the various duplex circuits. i 1

3. In a telegraph systemja plurality of duplex circuits, 7 duplex balance indicating means comprising an electromagnetic device responsive to each reversal of the transmitting switching means controlled by said electromagnetic device and responsive to currents resulting through unbalance conditions between {the real and artificial lines, indicat ing means controlled by said switching means for indicating'the characterof such unbalance," and switching means for conneeting said indicating means with said duplexeircuits periodically. p

4. In a duplex telegraph system, transmittingand receiving mechanisms. a leak circuitassociated with said transmitting mechanism and comprising a single polarized relay and means for maintaining said relay neutral during the idle moments of said transmitting mechanism, second polarized relay arranged to operate selectively in conjunction with said first relay when a difference in potentials in said system exists, and duplex balance indicating means arranged to operate with said second relay to indicate the character of the potential di'l? terences.

5. In a duplex telegraph system, transmitting and receiving mechanisms, a leak circuit associated with said transmitting means and comprising a single polarized relay and a condenser for maintaining said relay neutral during the idle moments of said transmitting mechanism, a second polarized relay arranged to operate selectively during the transmitting periods when a difference in potentials in said system exists, and a duplex balance indicating means arranged to operate with said second relay to indicate the character of potential differences.

6. In a duplex telegraph system, a real and an artificial line, transmitting and receiving mechanisms associated therewith, a leak circuit comprising a single polarized relay and a condenser, said relay being responsive to the reversals of current from said transmitting mechanism and said condenser being provided to maintain said relay neutral during the idle moments of said transmitting mechanism, a second polarized relay, said second relay being arranged to op erate selectively in conjunction with said first relay when a. difference in potentials of said lines exists, an armature on said second relay normally arranged in a neutral position, and duplex balance indicating means arranged to operate in conjunction with said armature to indicate the character of the potential differences.

In witness whereof, I hereunto subscribe my name this 25th day of September A. D., 1924.

JOHN H. BELL. 

